Credulous :: Credulous (a.) Apt to believe on slight evidence; easily imposed upon; unsuspecting.
Credulousness :: Credulousness (n.) Readiness to believe on slight evidence; credulity.
Incredulous :: Incredulous (a.) Not credulous; indisposed to admit or accept that which is related as true, skeptical; unbelieving..
Incredulous :: Incredulous (a.) Indicating, or caused by, disbelief or incredulity..
Incredulously :: Incredulously (adv.) In an incredulous manner; with incredulity.